<?php
class  Coordinate{
    private $arr  = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
    public function __call($one, $two)
    {
        $num = count($two);
        if($name == 'excel'){
            if($num == '1'){
                $num = count($two[0]);
                $num = $two[0] - 1;
                $this->arr["$num"];
            }
            if($num == '2'){
                $num = count($two[0]);
                $num = $two[0] - 1;
                $num1 = $two[1] - 1;
                $x1 = $this->arr["$num"];
                $y2 = $this->arr["$num1"];
                echo $x1.$y2;
;            }
        }
    }
}
$obj = new Coordinate;
$obj->excel('6','10');